Leica M4-P Instructions Manual page 15

Not For Resale – Free Download at http://homepage.ntlworld.com/joechan/manuals
The LEICA lenses have a fixed ring with
depth-of-field scale (10), a rotatable ring
for setting the focusing distance (11) and
an iris diaphragm ring (12).
The distance scale
The distance scale (11) indicates the dis-
tance on which the lens is set, and, in
connection with the depth-of-field scale
(10), the extent of the depth of field. The
distance is also important to the calculation
of the guide number during the use of flash
equipment.
The aperture scale
The aperture scale is internationally laid
down; the values have been chosen so
that the quantity of light reaching the film is
halved every time the lens is stopped
down one step. One aperture step is
equivalent to one step on the shutter
speed dial (5) regarding the adjustment of
the light quantity to which the film is
exposed. Like the shutter speed dial, the
lens diaphragm ring clicks into position
opposite each number (some diaphragm
rings also at half values). This will enable
you, after some practice, to identify the
setting of the diaphragm even in the dark.
15